The instant invention relates to a heat emitting unit in the form of a heater or cooler, and in particular to a heating unit to heat valve blocks and measuring instruments.
In industrial plants, often a number of measuring instruments connected via valve units to pipe lines are used. Pressure or flow measuring points for fluid media in the known arrangement of measuring transducers and upstream valve blocks, for example, are called pressure or flow measuring points. Out of doors these installations are normally mounted in protective instrument cabinets and the inside of such an instrument cabinet or the built-in instruments themselves are heated directly by thermostatically controlled heaters.
In general such a heater is expected to be highly efficient, to require little space, to be adaptable to different conditions, and to adjust precisely to a preset temperature while safety regulations, e.g. with respect to protection against contact and possibly explosion protection, are observed. Installation and possible retrofitting should be simple and assembly should be easy.
A known heating block (DE OS 36 33 682) consists of a main body and of a number of parallel, flat ribs projecting from the main body and attached to at least one side of the main body. The main body contains the heating element and the thermostatic setting. The main body is heated by the heating element and ribs with large surfaces and little thickness are provided at short intervals in order to offer as large a heat-radiating surface as possible. It has been found that the design or the attachment of such a rib system poses problems.
The possibility exists to produce the main body together with the ribs as a unit, in the form of a cast part. However, casting technology only permits to obtain relatively thick ribs with relatively great spaces between them, so that the requirements for the unit to occupy little space, to use a small amount of material, and to weigh little are not met satisfactorily.
In the DE OS 36 33 682 a completely different structure was therefore described, so that the prefabricated, punched-out sheet-metal ribs are incorporated into a main body in the casting process. In this process the sheet-metal ribs can project from the main body laterally, advantageously on both sides so that said main body can be kept relatively small. It was found, however, that such a process requires much effort and is expensive, due in particular to the time-consuming insertion of the sheet-metal ribs into the hot casting die.
It is furthermore well known that cooling bodies can be made of aluminum by means of extruders. In this process an extrusion profile with rib-shaped projections is drawn off. This profile is then cut off in disk form in the length desired for the cooling body. This process is not practically applicable in the instant case where long, narrow ribs are needed. It is known that technical difficulties arise with extruders when narrow ribs are to project far from a main profile billet because the flow of material at those points is hindered much more during draw-off than in the main profile billet. Furthermore, difficulties arise in the storage of such profiles to cool them because narrow ribs projecting far then risk becoming deformed and bent.
Furthermore, the basic configuration of the cooling body is determined in this process in such a manner that the ribs cannot extend beyond the main body laterally in the direction of the ribs because of the disk-shaped separation from the extruded profile billet. As is explained below, this restricts the possibilities of application considerably.
The production of a main body with shorter ribs by extrusion in order to obtain long ribs is widely known, and in this process the above-mentioned technical problems in manufacture do not arise. Furthermore, a second body, also technically well obtainable provides shorter ribs at proper intervals, is produced by extrusion. These two bodies are joined together at their free rib ends and are placed on top of each other in comb fashion so that cooling ribs are obtained in lengths that are equal to the sum of the lengths of two ribs placed on top of each other. However this necessarily results in closed cooling channels which are open only in one direction of the ribs, reducing the application possibilities of such devices.
It is the object of the instant invention to create a heat emitting unit in the form of a heating or cooling body in which the relatively long and numerous ribs can be realized technically in a satisfactory manner and can be produced inexpensively, whereby the possibility of allowing the ribs to project laterally beyond the main body should in particular be given so as to ensure universal applicability.